In Switzerland, Jet lag is the condition in which as a result of travelling across multiple time zones quickly, your inner sense of daily rhythms no longer matches the local rhythms at your destination. People normally live in a 24-hour rhythm. While we sleep, our heart and breathing rates slow, our blood pressure drops, our muscles relax and our mental and psychomotor efficiency decline significantly. Light is one of the main guides that our body uses to maintain its sense of time. The brightness of day and the darkness of night are the prime means by which we manage our “internal clock”.
A rapid journey through multiple time zones will put our internal clock out of sync with the local day-and-night rhythm. Our internal clock will be confused, because it now needs to adapt to a new time, a new light-and-dark rhythm and a new activity/inactivity cycle. And it’s not only our sleep/wake rhythm that is upset here: the shift also affects many other regular bodily functions that are subject to the same 24-hour cycle.